(1) Field of Invention
The present invention generally relates to surveying portable sensor nodes.
(2) Description of the Prior Art
Acoustic underwater ranges often use a pinger-based system for localization and tracking. This system involves an acoustic device being tracked that sends out a regular encoded acoustic signal known as a ping that can be received by hydrophones positioned at known locations. Incoming acoustic energy from a ping is received by the hydrophones and transmitted to digital signal processing nodes. These processors turn raw acoustic data into time-tagged detection report information. This detection report includes the ping's encoded frequency, ping encoding type, ping index, time of arrival of each ping, and the receiving hydrophone. Other information can also be included. A tracking software system receives all the detection reports relevant to a particular target over all the hydrophones on the range. Using the known position of those hydrophones, the environmental data and iterative numerical algorithms, the software produces a candidate location and time of emission for the received ping.
Some surveying systems employ a marine vehicle with transponders to send out signals and detect echoes as it passes by objects in the water. Portable ranges are known that are self-contained training systems embedded with bottom mounted transponders. These portable ranges include multiple bottom mounted transponders and a surface link to a support vessel and the necessary shipboard systems. A basic portable range operational configuration consists of an array of seven bottom-moored transponders, and a range support vessel having a shipboard processing unit and a satellite link to a shore-based remote display center. The bottom moored transponders must be emplaced at known locations. The transponders detect tracking signals emitted from the exercise participants and transmit data via an acoustic data uplink. The transmission can be received by a dunking head hydrophone suspended from the range support vessel. The shipboard processing unit processes the data and generates a detection report in a format compatible with the tracking software. The shipboard processing unit can also control and monitor the status of the transponders through acoustic commands.
The above mentioned methods of establishing a range incur high logistical costs and time because of the requirement that the bottom mounted transducers be emplaced at known locations. Therefore, there is a need for an underwater range having self-surveying portable sensor nodes and a base unit that can determine their locations with minimal outside support.